Pipe joint seal



tenteci Nov. 7, 1939 PATENT OFFICE 2,179,202 PIPE .iorN'r SEAL Albert W. Simpson, Dormont, Pa., assigner to National Tube New Jersey Company, ai corporation oi Application June 23, i937, Serial No. Milii i cnam..l (pi. 2st-isi) This invention relates to pipe joint seals and more particularly to threaded pipe joint seals.

Threaded pipe joints are not fluid-tight, in

spite ci the fact that threading requirements `and specifications have become extremely rigid and the ine degree of accuracy with which threads are made under present-day commercial threading practice. The use of a seal is particularly necessary where the joined tubular sections convey gases under high pressures. Many attempts have been made to render threaded pipe jointsfluid-tightfunder heavy pressure but none have been made that would successfully and economically seal a standard pipe and coupling joint.

lit is accordingly an object of the present invention to provide a fluid-tight threaded pipe joint.

A further object of the present invention is to provide a fluid-tight seal for threaded pipe joints.

The foregoing and further objects of the present invention will be apparent after referring to the drawing, in which:

Figure l is a fragmentary sectional elevation.

Figure 2 is a sectional view on the line II-PII of Figure l.

Referring more particularly to the drawing, the numeral 2 designates the threadedjoint sealing gasket of my invention which is composed of a softer metal than the metal of tubular joint sections such as, for example, copper. The numerals 3 and 4 designate a pipe and coupling' joined together by conventional tapered threads t. As is shown in Figure 1 of the drawing, the pipe i has a slightly tapered unthreaded end portion t of substantially smaller diameter than the outside diameter of the pipe 3. The taper of the end section B should be substantially the same as the taper of the threads 5.

have a slightly smaller diameter than the mean outside diameter of the tapered end portion 6. It

is not necessary that the gasket 2 be tapered on either its interior or exterior surface as the pressure between the pipe 3 and coupling [in the assembled joint willcause it to conform to the taper Aof the pipe and coupling. The outside diameter or periphery of the gasket 2 is provided with screw-threads 8 of substantially the sam pitch as the threads 5 and the overall diameter of the gasket, after being threaded, is substantially the same` as the overall diameter of the threaded portion of the pipe 3 adjacent the unthreaded portion 6. Consequently the gasket 2 can be easily screwed several turns within the The inner surface of the gasket 2 should coupling i which will give ample space to insert the pipe 3 to start threading it therewithin. Upon ycontinued screwing together of the pipe 3 and coupling 4, the gasket 2 will be screwed forwardly within the coupling by reason oi the frictional engagement between it and the inner extremity of the pipe 3 until the gasket 2 is tightly engaged by the tapered threads of the coupling As the resistance to further turning'of the gasket 2 becomes greater than the frictionai engagement between it and the pipe, the tapered portion 6 of the pipe will feed forwardly into the interior l of the gasket 2, thereby expanding the gasket into tighter engagement with the coupling until ther gasket is disposed upon the tapered portion 6, this forming a `fiuid-tight seal between the threads 8 of the gasket 2 and the threads 5 of the coupling, and also between the interior 1 of the gasket 2 and the tapered portion 6 of the pipe 3, whereby the joint is eifectually sealed. If further relative screwing of the pipe 3 and coupling 4 are necessary to seat them firmly together, the gasket 2 will be forced to move inwardly of the coupling by the relative movement of the pipe and coupling and, due to the taper of the threads 5,-will thereupon become more tightly compressed between the threads 5 and the .end 6 of the pipe 3. However, since the overall .into the coupling than the pipe. Hence, after the gasket has ceased to rotate with the pipe, the continued rotation of the pipe necessary to seat it rmiy within the coupling will cause the tapered portion 5 to move into the interior of the gasket which will be expanded over the tapered portion E. The gasket 2 will then be under high compressionbetween the threads of the coupling l and the tapered portion 6 of the pipe, thereby forming an eifective seal. l

It will be noted that a specially machined coupling' having a sealing member disposed within a groove therein, or threads machined to such a fine degree of accuracy that a gasket can be` compressed between the ends of the pipe within a coupling or between the end of the pipe and end of the pipe to provide a tapered portion thereat. Bythe use of a sealing gasket, as described in conjunction with a pipe having an unthreaded and slightly tapered end portion, a seal will be eiected at the end of the pipe at any position within the coupling where the threads of the pipe and coupling have become iirmly seated. Due to the normal variations in dimensions of threaded pipe and coupling members, this seating position will vary within wide limits but, by following the teachings of my invention a positive uid-tight seal will always be obtained in an extremely simple manner as compared to heretofore known methods.

'I'his form of seal is particularly effective for joints subjected to great longitudinal stresses which sometimes cause the pipe and coupling member to be stretched. Even if this occurs in a joint of the present invention the effectiveness of the seal is not diminished as the gasket is still i'lrmly compressed between the coupling and the tapered portion of the pipe despite a slight slippage between the gasket and the tapered portion of the pipe.

While I have shown and described a specic embodiment of my invention it will be understood that I do not Wish to be limited exactly thereto, since various modifications may be made within the scope of the following claim.

I claim:

A threaded pipe joint comprising an internally threaded metallic tubular member and an ex-- ternally threaded metallic tubular member adapted to telescope therewith, said externally f threaded member having an unthreaded annular portion of reduced diameter adjacent its outer extremity, said unthreaded annular portion being frusto-conical toward the extremity of said externally threaded member and adapted for disposal within said internally threaded member, the threads of the internally threaded member and the threads of the externally threaded member being tapered and complementary to each other, and a metallic sealing gasket of softer metal. than the metal of both the internally threaded member and the externally threaded member, said metallic sealing gasket being annular and provided with a bore of the same form as the frusto-conical portion of said externally threaded member, the perimeter of said metallic sealing gasket being prethieaded with the same pitch as `the threads of the internally threaded member, the bore of said metallic sealing gasket being originally of slightly smaller diameter than the diameter of the frusto-conical portion of the externally threaded member, said metallic sealing gasket being adapted for expansiononto the frusto-conical portion of the externally threaded member by positioning the latter within the internally threaded member and rotating the same; whereby a fluid-tight seal is formed by the compression of the prethreaded metallic sealing gasket between the threads of the internally threaded member and the frusto-conical extremity of the externally threaded member.

ALBERT W. SIMPSON. 

